package com.exm.collectcodenew.juc.fj;

import java.util.concurrent.*;

public class CountTask extends RecursiveTask<Integer> {
    private static final int THRESHOLD =2;//阈值
    private int start;
    private int end;
    public CountTask(int start,int end){
        this.start=start;
        this.end=end;
    }

    @Override
    protected Integer compute() {
        int sum=0;
        //如果任务足够小就计算任务
        boolean canCompute= (end-start)<=THRESHOLD;
        if(canCompute){
            for(int i =start;i<=end;i++){
                sum+=i;
            }
        }else{
            //如果任务大于阈值，就分裂成两个子任务计算
            int middle=(start+end)/2;
            CountTask leftTask=new CountTask(start,middle);
            CountTask rightTask=new CountTask(middle+1,end);
            //执行子任务
            leftTask.fork();
            rightTask.fork();
            //等待子任务执行完，并且得到结果
            int leftResult=leftTask.join();
            int rightResult=rightTask.join();
            //合并子任务
            sum=leftResult+rightResult;

        }
        return sum;
    }

    public static void main(String[] args) {
        ForkJoinPool forkJoinPool=new ForkJoinPool();
        //生成一个计算任务，负责计算1+2+3+4
        CountTask task= new CountTask(1,4);
        //执行一个任务
        Future<Integer> result =forkJoinPool.submit(task);
        try {
            System.out.println(result.get());
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        } catch (ExecutionException e) {
            throw new RuntimeException(e);
        }
    }
}
